Re: [PULL 02/18] i386/kvm/cpu: Init SMM cpu address space for hotplugged CPUs

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 10/29/2025 3:01 PM, Zhao Liu wrote:
>> diff --git a/hw/i386/x86-common.c b/hw/i386/x86-common.c
>> index 7512be64d67..5716191fff1 100644
>> --- a/hw/i386/x86-common.c
>> +++ b/hw/i386/x86-common.c
>> @@ -183,6 +183,17 @@ void x86_cpu_plug(HotplugHandler *hotplug_dev,
>>           fw_cfg_modify_i16(x86ms->fw_cfg, FW_CFG_NB_CPUS, x86ms->boot_cpus);
>>       }
>>   
>> +    /*
>> +     * Non-hotplugged CPUs get their SMM cpu address space initialized in
>> +     * machine init done notifier: register_smram_listener().
>> +     *
>> +     * We need initialize the SMM cpu address space for the hotplugged CPU
>> +     * specifically.
>> +     */
>> +    if (kvm_enabled() && dev->hotplugged && x86_machine_is_smm_enabled(x86ms)) {
>> +        kvm_smm_cpu_address_space_init(cpu);
>> +    }
>> +
> 
> Unfortunately, the original KVM SMM patch caused this bug, but even
> more unfortunately, CPU_FOREACH in the machine_done callback is more
> fragile than I originally anticipated, now requiring more hack checks to
> fix. :-(
> 
> IMO, the root of the chaos is that KVM SMM doesn't do this in the CPU
> context like TCG did for a long time. I'll find time to sort all this
> out.

I had this idea before. It needs to move the initialization of KVM SMM 
MemoryRegion a bit earlier at least. And it seems to require more time 
than I expected, especially the effort to test the SMM functionality 
after the change. So I went with the most straightforward fix.

It will be great if you can find time to clean it up. Looking forward to it.

> Regards,
> Zhao
>